The detection and/or monitoring of analyte levels, such as glucose, ketones, lactate, oxygen, hemoglobin A1C, or the like, can be vitally important to the health of an individual having diabetes. Diabetics generally monitor their glucose levels to ensure that they are being maintained within a clinically safe range, and may also use this information to determine if and/or when insulin is needed to reduce glucose levels in their bodies or when additional glucose is needed to raise the level of glucose in their bodies.
Growing clinical data demonstrates a strong correlation between the frequency of glucose monitoring and glycemic control. Despite such correlation, many individuals diagnosed with a diabetic condition do not monitor their glucose levels as frequently as they should due to a combination of factors including convenience, testing discretion, pain associated with glucose testing, and cost.
Systems have been developed for the automatic monitoring of analyte(s), like glucose, in bodily fluid such as in the blood stream, in interstitial fluid (“ISF”), or in other biological fluid. Some of these analyte measuring systems are configured so that at least a portion of a sensor control device is positioned below a skin surface of a user, e.g., in a blood vessel or in the subcutaneous tissue of a user, so that the monitoring is accomplished in vivo. As such, these systems are typically referred to as “in vivo” monitoring systems. They are in contrast to “in vitro” systems that contact a sample outside the body (or rather “ex vivo”) and typically include a meter device that has a port for receiving an analyte test strip carrying bodily fluid of the user, which can be analyzed to determine the user's blood sugar level.
In vivo analyte monitoring systems can be broadly classified based on the manner in which data is communicated between the reader device and the sensor control device. One type of in vivo system is a “Continuous Analyte Monitoring” system (or “Continuous Glucose Monitoring” system), where data can be broadcast from the sensor control device to the reader device continuously without prompting, e.g., in an automatic fashion according to a broadcast schedule. Another type of in vivo system is a “Flash Analyte Monitoring” system (or “Flash Glucose Monitoring” system or simply “Flash” system), where data can be transferred from the sensor control device in response to a scan or request for data by the reader device, such as with a Near Field Communication (NFC) or Radio Frequency Identification (RFID) protocol.
Both in vivo and in vitro systems typically contain a power supply and electronics for performing the blood sugar analyses. The systems are provided to the user through typical medical device distribution channels, and these channels can become filled with inventory, which could result in a device residing on the shelf for a lengthy duration of time between manufacture and first use. A concern exists that, during this time, any on-board power supply, such as a battery, might become drained of its current supplying capacity. This concern is exacerbated by the trend towards ever smaller and more power efficient devices, which use smaller and less powerful batteries.
In the past, battery leakage in a product residing on the shelf was minimized by the placement of an insulator between the battery and the physical electrical contact through which the battery supplies current. For example, a removable paper insulator was placed directly between the battery and the device's battery contact, such that a user could remove the insulator and thereby initiate electrical contact just prior to first use. However, this solution requires that the user has physical access to the battery, which may not be the case in a design where the battery is located wholly within the device housing in an inaccessible fashion. This solution also requires an additional step of user intervention prior to first use of the device, which can negatively impact the marketability of the device.
In other cases, the battery was placed in direct electrical contact with the leads of the device, but a control circuit was used to prevent the battery from connection to the electrical load of the on-board circuitry. Whenever the device was activated, the control circuit would form a closed path between the battery and the electrical load of the device to supply power. Whenever the device was deactivated, the control circuit would open the path between the battery and the electrical load so as to disconnect the battery and minimize any current leakage therefrom.
However, new applications have arisen, such as with respect to in vivo monitoring, where it has become desirable to leave the battery in a connected state at all times, even when the in vivo monitoring device is deactivated, or powered off. While such a device does not draw current to power its electrical circuitry in the deactivated state, the battery remains connected and the control circuit continues to draw power in the form of leakage current. Prior control circuits suffer from leakage levels that are too high to permit the battery to remain in a connected state when the monitoring device is deactivated.
Accordingly, needs exist for improved in vivo and in vitro analyte monitoring devices having increased shelf-life, greater power efficiency, greater flexibility to be used in new analyte monitoring applications, and greater control of performance.